This invention relates to a gooseneck, which is also referred to as a tubing guide, and more particularly to a tubing guide for directing coiled tubing into a coiled tubing injector apparatus. Reeled or coiled tubing has been run into completed wells for many years for performing certain downhole operations. Those operations include, but are not limited to, washing out sand bridges, circulating treating fluids, setting downhole tools, cleaning and internal walls of well pots, conducting producing fluids or lift gas, and a number of other similar remedial or production operations. The tubing utilized for such operations is generally inserted into the wellhead through a lubricator assembly or stuffing box. Typically, there is a pressure differential on the well so that the well is a closed chamber producing oil or gas or a mixture thereof from the pressurized well. The tubing that is inserted into the well is normally inserted through a lubricator mechanism which seals the well for pressure retention in the well.
The tubing is flexible and can bend around a radius of curvature and is normally supplied on a drum or reel. The tubing is spooled off the reel and inserted into a coiled tubing injector assembly. The coiled tubing injector assembly essentially comprises a curvilinear gooseneck, or tubing guide and a coiled tubing injector apparatus positioned therebelow.
The curvilinear tubing guide forms an upper portion of the injector assembly while the coiled tubing injector apparatus forms a lower portion thereof. Most coiled tubing injector apparatus utilize a pair of opposed inlet drive chains arranged in a common plane. Such drive chains are made up of links, rollers and gripper blocks. The drive chains are generally driven by sprockets powered by a motor which is a reversible hydraulic motor. The opposed drive chains grip the coiled tubing between them. The drive chains are backed up by linear beams, also referred to as pressure beams, so that a number of pairs of opposed gripping blocks are in gripping engagement with the tubing at any given moment. Coiled tubing injector apparatus are shown in U.S. Pat. No. 5,094,340 to Avakov, which is incorporated herein by reference for all purposes, and U.S. Pat. No. 4,655,291 to Cox, which is likewise incorporated herein for all purposes.
A typical tubing guide has a curvilinear first frame portion with a set of rollers or tubing guide strips thereon which support and guide the tubing as it is moved through the injector. Spaced from the first frame portion is a second frame portion which may also have a set of rollers thereon, which are on the opposite side of the tubing from the first set of rollers and which also act to guide the tubing. The tubing guide is pivotable for easy alignment with the tubing reel. The radius of curvature of the typical tubing guide is constant and is typically smaller than the residual or natural radius of curvature of the coiled tubing in its free state after it has been spooled off the reel. The rollers therefore force the tubing to bend to match the curvature of the tubing guide and to straighten the tubing so that it is substantially vertical when it exists the tubing guide and enters the coiled tubing injector apparatus therebelow. The bending stresses experienced by the tubing each time it is deformed or bent and injected into the well decrease the life of the coiled tubing.
During a typical coiled tubing job, the pipe may be subjected to at least six bending stages. Going into the well, the first bending stage occurs when the plastically shaped tubing leaves the tubing reel and is straightened on its way to the tubing guide. The second is the bending of the now straightened coiled tubing around the tubing guide. The third is the straightening of the coiled tubing that has been bent around the tubing guide through the tubing injector so that it can be directed into the well. Out of well deformation occurs as the straightened tubing is withdrawn from the well through the tubing injector and deformed around the tubing guide. Additional deformation occurs when the bent tubing leaves the tubing guide and is straightened somewhat on its way to the reel. The third and final deformation is when the straightened tubing is wrapped onto the reel. Thus, coiled tubing may see six bending stages or deformations per trip in and out of the well. The low cycle fatigue generated by the deformation is a limiting factor in the life expectancy of a coiled tubing string.
Tubing guides have evolved in shape and size. The first tubing guides were created to provide a framework around which to bend pipe to lead it into the injector. It became apparent that the radius of the tubing guide had a definite impact on the life expectancy of the tubing, so that larger radius tubing guides were designed to increase the fatigue life of the tubing. The first large radius tubing guides were, however, like their predecessors a continuous single radius. Many present day tubing guides utilize a continuous single radius. Because the size of the tubing guide is limited by a number of factors, and because of various requirements during rig-up, namely, the position of the coiled tubing relative to the tubing guide, large radius tubing guides, while having better fatigue benefits than small radius tubing guides, still create fatigue problems that impact the life of the coiled tubing and in some instances provide difficulties in the installation of the tubing.
Typically, to install the coiled tubing, the end thereof is stabbed into the tubing guide at or near the base of the tubing guide assembly to help direct the tubing into the injector. Very often curvature of the tubing will be such that once it is stabbed, there is a fairly large distance between the coiled tubing and the tip or end of the tubing guide. Thus, it is necessary to apply pressure to the coiled tubing to pull it down to the tubing guide. One manner of doing so is using a hand winch, which is commonly referred to as a come-along, to pull the tubing down to the tubing guide. Once the tubing has reached the tubing guide, rollers or other means are utilized to hold the tubing to the tubing guide so that it can then be directed around the tubing guide into the injector. Such procedures are time consuming, can sometimes be dangerous and can also increase the bending stresses in the tubing.
One prior art resolution to the problems associated with the continuous radius tubing guide is the variable radius tubing guide such as that shown in U.S. Pat. No. 5,799,731 to Avakov et al., assigned to the assignee of the present invention, the details of which are incorporated herein by reference. The variable radius tubing guide shown therein combines a larger radius near the base of the tubing guide with a small radius near the tip of the tubing guide. The smaller profile at the tip allows more versatility during rig-ups while the larger bend radius accommodates the natural radius of larger coiled tubing as it moves off the reel. While the tubing guide shown in the ""731 patent addresses the problem of fatigue on coiled tubing, there is still a need in the industry for a tubing guide that will lessen further the bending experienced by the tubing, thus lessening the fatigue effects. Thus, there is a need for an improved tubing guide and a method of directing tubing into the injector which will lessen bending and thus lessen the fatigue effect on the tubing and which will provide for easier installation of the tubing around the tubing guide.
The present invention provides an improved tubing guide for directing coiled tubing into a well. The tubing guide comprises a base and a frame extending therefrom. The tubing guide is a conformable tubing guide and thus has a conformable or adjustable shape. The shape of the tubing will conform depending on the natural radius of curvature of the tubing being placed thereon, so that the tubing can follow a path that more nearly approximates the residual or natural radius of curvature of the tubing. The tubing carrier preferably is a segmented tubing carrier comprising a plurality of frame segments. Each of the frame segments is connected near a rear end thereof to a location near the forward end of the adjacent segment. The segments are pivotably connected to one another so that the tubing carrier can conform or adjust to any number of shapes thereby allowing the carrier to conform to more nearly approximate the natural radius of curvature of the tubing placed thereon.
The tubing carrier preferably has first, second, third and fourth segments. The fourth segment is connected to the base of the tubing guide. The first segment is pivotably connected to the second segment near the rear end of the first segment. Likewise, the second segment is pivotably connected near its rear end to the third segment and the third segment is pivotably connected at its rear end to the fourth segment. Pivotal movement, or rotation of the segments, is limited to a maximum or minimum rotation so that the carrier will have a fully closed and a fully open or rotated position. By conforming or adjusting, the tubing guide will alleviate some of the bending stresses normally associated with placing a tubing on a tubing guide and directing the tubing into a coiled tubing injector by allowing the path of the coiled tubing to more nearly approximate its natural, or residual shape or radius. The present invention also provides for an easier installation or rig-up since the tubing carrier segments can be rotated so that the tubing carrier can conform to the shape of the tubing, or to at least partially conform to the shape of the tubing, to eliminate, or at least to lessen the amount of mechanical force that must be applied to the coiled tubing to bring the tubing into engagement with the tubing guide.
It is therefore a general object of the present invention to provide an improved tubing guide which provides easier rig-up and installation and which lessens the bending stresses normally associated with the operation of the tubing guide. Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art in view of the drawings herein and a reading of the description of the preferred embodiment which follows.